There is a continued need for expanding the flexibility of available fuels for improving emission quality of internal combustion engines. At the same time, there is pressure to maintain available power performance of these engines, while maintaining maximum or near maximum fuel economy. Those pressures apply to engines fueled with alternative fuels, such as natural gas, as well as to those fueled with gasoline.
This need is compounded by the need to provide a durable, gas phase injector that provides sufficient flow for future performance and fuel efficiency requirements, and that can be applied as an injector for direct injection into the combustion chamber of the engine.
Emission quality also encompasses hydrocarbon emissions when the engine is not operating, generating the expectation of both high speed response of the injector and near zero leak of the gas phase fuel when the injector is not energized. The materials that allow for the needed leak performance can be best met by available elastomeric compounds which have limited high temperature survivability. A solution to this is by use of a barrier or another valve in addition to the metering valve to isolate the leak prevention materials from the high gas temperatures of the combustion chamber in which the injector is positioned to supply fuel. This has been implemented with limited success for natural gas applications and some air injection applications.